OBJECTIVE To identify the mechanisms which mediate the psychosocially induced suppression of the stress hormone cortisol in socially subordinate, reproductively suppressed female marmosets. RESULTS Chronic suppression or elevation of the stress hormone cortisol is often associated with neuropsychiatric disorders in humans. As a possible model for these endocrine disturbances, we have been investigating the causes of chronic cortisol suppression in socially subordinate, reproductively suppressed female marmosets. To date, we have examined (1) baseline adrenocorticotrophic hormone (ACTH) levels, to determine whether cortisol suppression is caused by reduced pituitary stimulation of the adrenal cortex; (2) ACTH and cortisol responses to dexamethasone, a synthetic glucocorticoid, to determine whether subordinate females exhibit enhanced sensitivity to glucocorticoid negative feedback; and (3) cortisol responses to exogenous ACTH, to determine whether cortisol suppression is associated with reduced adrenal sensitivity. Results thus far indicate that neither baseline plasma ACTH levels nor the pituitary and adrenocortical responses to dexamethasone differ between groups. Howev er, subordinate females show a blunted adrenocortical response to exogenous ACTH. These results suggest that reduced adrenocortical responsiveness is an important component of adrenocortical suppression in subordinate females. FUTURE DIRECTIONS We will continue to investigate the physiological, biochemical, and molecular mechanisms of adrenocortical suppression in subordinate female marmosets as a model of adrenocortical dysregulation in human neuropsychiatric disorders. KEY WORDS dominance, subordination, ovarian cycle, adrenal cortex, adrenocorticotrophic hormone, glucocorticoids FUNDING NIMH MH53709-01 PUBLICATIONS Saltzman, W., N.J. Schultz-Darken, F.H. Wegner, D.J. Wittwer, and D.H. Abbott. 1998. Suppression of cortisol levels in subordinate female marmosets Reproductive and social contributions. Hormones and Behavior 33:58-74. [J] Abbott, D.H., W. Saltzman, N.J. Schultz-Darken, and P.L. Tannenbaum. 1998. Adaptations to subordinate status in female marmoset monkeys. Comparative Biochemistry and Physiology Part C 119:261-274. [J]